Mono-n-benzyl-diamino-phenyl compounds



Feb. 15, 1966 M. GREEN ETAL 3,

MONO-N-BENZYL-DIAMINO-PHENYL COMPOUNDS Filed Oct. 17. 1962 lO- SUPPORT II ----PHOTOSENSITIVE LAYER Iz PROCESSING COMPOSITION l3 IMAGE-RECEIVING LAYER l4 T SUPPORT FIG. I

l5- SPREADER SHEET T ::1:; PROCESSING COMPOSITION I| PHOTOSENSITIVE LAYER |3 IMAGE-RECEIVING LAYER I4 SUPPORT FIG. 2

INVENTORS Q MMW ATTORNEYS United States Patent Office 3,235,599 Patented Feb. 15, 1956 3,235,599 MONO-N-BENZYL-DIAMINO-PHENYL COMPOUNDS Milton Green, Newton Center, Meroe M. Morse, Boston, and Myron S. Simon, Newton Center, Mass., assignors to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware Filed Oct. 17, 1962, Ser.No. 231,185

6 Claims. (Cl. 260-5709) This application is a continu-ation-in-part of application Serial No. 861,127, file-d December 21, 1959, now US. Patent No. 3,091,530, issued May 28, 1963.

The present invention relates to photography and more particularly to compositions, products, and processes useful in the development of selectively photoexposed photosensitive silver halide elements, and especially to compositions and products useful in diffusion transfer processes, particularly in high sp eed diffusion processes wherein a silver halide photosensitive emulsion has been underexposed in relation to its A.S.A. Exposure Index, that is, to processes for deriving useful photographic transfer prints from latent images formed at low exposure levels.

In diffusion transfer processes, for the formation of positive silver images, a latent image contained in a selectively photoexposed photosensitive silver halideemulsion is developed. Almost concurrently therewith, a soluble silver complex is obtained by reaction of a silver halide solvent with the unexposed and undeveloped silver halide of said emulsion. Preferably, the photosensitive silver halide emulsion is developed with a processing composition in a viscous condition, which is spread betweenthe photosensitive element comprising the silver halide emulsion and a print-receivingelement comprising, preferably, a suitable silver precipitating layer. The processing composition effects development of the latent image in the emulsion and substantially contemporaneous therewith forms a soluble silver complex,.for example, a thiosulfate or thiocyanate complex, with undeveloped silver halide. This soluble silver complex is, at least in part, transported in the direction of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form the desired positive image therein.

High speed diffusion transfer processes are generally of the type in which, for example, a silver halide stratum containing a latent image formed at a low exposure level and an image-receiving stratum, in superposition, are subjected to a processing composition containing a-highly energetic silver-halide developing agent and a silver halide solvent in order torform a silver transferprint inand/or on the image-receiving stratum. The silver halide developing agent serves to reduce photoexposcd silver halide to silver in the photosensitive emulsion stratum. The silver halide solvent reacts with unreduced silver halide to form the aforementioned soluble silver complex which, in turn, is reduced in the presence of the image-receiving stratum to form the desired positive print. The photosensitive stratum'may be subsequently dissociated from the image-receiving stratum. In accordance with a preferred embodiment of the present invention, the silver halide stratum may be underexposed in relation to its rated A.S.A. Exposure Index and the silver halide developing agent is specifically selected from the class hereinafter set forth.

Preferably, the image-receiving stratum is in such condition as to cause silver reduced there, in comparison with silver reduced in ,the photosensitive silver halide stratum, to possess very high covering power, that is, opacity per given mass of reduced silver. This high covering power is achieved by accumulating the silver deposited in the silver-receptive stratum in unusually dense masses, for example, by minimizing the thickness of the stratum in which the silver-receptive material is contained.

The high speed diffllSiOn. transferprocesses set forth herein provide readily available and uniquely simple processes for producing satisfactory highv quality of good resolution and trivial granularity at 'low illumination levels, for example, at overall exposures that are equivalent to A.S.A. ExposureIn-dices of 600 and up,

Accordingly, objects of the present invention are to provide: novel products, developer compositions, and processes employing such products and developer compositions, for the development of selectively photoexposed silver halide emulsions; novel products and developer compositions useful in high speed diffusion transfer processes wherein a selectively photoexposed silver halide emulsion has been substantially un-derexposed in relation to its A.S.A. Exposure Index; and to employ, in processes of the aforementioned type, a silver halide developing agent selected from the class hereinafter set forth.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the severalsteps and the relation and order of one or more of such-steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects 0f the present invention, reference should be had to the-following detailed description taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is adiagrammatic enlarged cross-sectional view illustrating the association of elements during one stage of the performance of a diffusion transfer process, for the production of positive silver prints, the thickness of the various materials being exaggerated; and

FIGURE 2 is a view similar to that of FIGURE 1 illustrating the association of elements during one stage of the performance of another diffusion transfer process, for the production of positive silver prints.

Amidol (2,4-diarninophenol hydrochloride) is an energetic silver halide developing agent which has received only limited use in general photography due to its rapid oxidation in solution. On the other hand, amidol may be employed in diffusion transfer processes by incorporating it in a ruptura'ble container which is substantially airtight. It has been found, however, that use of amidol in diffusion transfer processes gives rise to a deeply colored oxidation product which will stain the hands and clothes of the person performing the transfer process. This deeply colored oxidation product apparently is formed after the processing composition has been spread between the photosensitive and image-receiving elements. The layer of processing composition preferentially adheres to the developed photosensitive element, and will stain ob jects, e.g,, hands or clothes, with which it comes into contact.

It has been found that the silver halide developing agents of this invention possess many of the desirable properties of amidol but do not give rise to highly colored oxidation products in diffusion transfer processes. These new silver halide developing agents also are substantially more stable than amidol when employed in tray or tank processing in general photography.

The novel class of silver halide developing agents of the present invention maybe represented by the formula:

wherein either R or R comprises a benzyl group, or a hydroxybenzyl group, and the remaining R or R is hydrogen; and the nuclear substituted halogen derivatives, preferably the nuclear substituted chlorine derivatives thereof and less preferably the bromine and iodine nuclear substituted derivatives, wherein a halogen atom is substituted on the benzene ring of the diaminophenol group.

A preferred class of silver halide developing agents within Formula (A) may be represented by the formula:

wherein Z is hydrogen or chlorine and one of R and R is a hydroxybenzyl group and the other of R and R is hydrogen.

The developing agents of the present invention may be employed in the form of their acid addition salt-s, such as the hydrochloride.

The following compounds are examples of silver halide developing agents within the scope of the present invention:

NHQ

4-amino-2-benzylamino-phenol 2-amin0-4-benzylamino-phenol NHGHz-QOH 4-amin0-2- p-hydroxybenzylamino) -phenol lamina-2 m-hydr0xyb enzylamino) phenol NHGHa- 2-amino-4- m-hydroxybenzylamino) -phen01 on Q-NH,

NHOH

2-amino-4- p-hydroxybenzylamino -pheno1 4-amin0-6-chlor0-2- (p hydroxybenzylamino) -pheno1 A preferred method of preparing the compounds of Formula A comprises reacting either an o-amino-pnitor-phenol or a p-amino-o-nitro-phenol with either benzaldehyde or hydroxybenzaldehyde to provide a compound of formula:

Synthesis of 4-amino-2-benzylamin0-phen0l In a 250 cc. Erlenmeyer flask were placed 15.4 grams of 2-amino-4-nitro-phenol and 10.6 grams of benzaldehyde. The mixture reacted almost immediately. The

product, 2-(N-benzylidene-amino)-4-nitro-phenol, was crystallized from alcohol and dried. The product melted at 196 to 198 C. [Yield 94.5%.]

A mixture comprising 12.1 grams of the Schiff base product, 6 grams of 5% palladium on barium sulfate, and 200 cc. of ethyl acetate was hydrogenated in a Parr shaker bottle at an initial pressure of approximately 35 pounds per square inch. The bottle was shaken until the theoretical amount of hydrogen was absorbed (20 to 30 minutes). The mixture was then filtered through a Celite pad into concentrated hydrochloric acid. The product, 4-amino-2-benzylamino-phenol, a white solid, precipitated spontaneously from the acid solution as the hydrochloride. The precipitate was separated 'by filtration, washed with ether and dried in a vacuum desiccator over potassium hydroxide. [Yield 89.2%.]

EXAMPLE 2 Synthesis of 2-amin0-4-benzylamino-phenol 4-amino-2-nitro-phenol was reacted with benzaldehyde to provide 4-(N-benzylidene-amino)-2-nitro-phenol, melting point 104 to 105 C., which then was reduced to provide the desired product, according to the procedures of Example 1.

EXAMPLE 3 Syn thesis of 4-amin0-2- (p-hydroxybenzy lamina) -phenl 2-amino-4-nitro-phenol was reacted with p-hydroxybenzaldehyde to provide 2-(N- [p-hydroxybenzylidene]- amino)-4-nitro-phenol, melting point 233 to 235 C., which in turn was reduced to provide the desired product, according to the procedures of Example 1.

EXAMPLE 4 Synthesis of 4-amino-2-(m-hydroxybenzylam'ino)-phen0l Z-amino-4-nitro-phenol was reacted with m-hydroxybenzaldehyde to provide 2- (N-[m-hydroxybenzylidene] amino)-4-nitrophenol, melting point 197 to 200 C., which in turn was reduced to provide the desired product, according to the procedures of Example 1.

EXAMPLE 5 Synthesis of 2-amino-4-(m-hydroxybenzylam'ino)-phen0l 4-amino-2-nitro-phenol was reacted with p-h'ydroxybenzaldehyde to provide 4-(N-[m-hyd-roxybenzylidene]- amino)-2-nitro-phenol, melting point 158 to 168 C., which in turn was reduced to provide the desired product, according to the procedures of Example 1.

EXAMPLE 6 Synthesis of 2-aminO 4-(p-hydroxybenzylamino)-phen0l 4-arnino-2-nitro-phenol was reacted with p-hydroxybenzaldehyde to provide 4-(N-[p-hydroxybenzylidene1- amino)-2-nitro-phenol, melting point 188 to 193 C., which in turn was reduced to provide the desired product, according to the procedures of Example 1.

EXAMPLE 7 Synthesis of 4-amin0-6-chl0r0-2-(p-hydroxybenzylamino) phenol 2-amino-6-chloro-4-nitro-phenol was reacted with phydroxybenzaldehyde to provide 6-chloro-2-(N-[p-hydroxybenzylidene]-amino)-4-nitro-phenol, melting point 235 to 237 C., which in turn was reduced to provide the desired product, according to the procedures of Example 1.

The novel silver halide developing agents of the present invention are useful in conventional b-lack-and-white developement and in diffusion transfer processes, both dye and silver. Examples of such processes are disclosed in US. Patents Nos. 2,543,181 and 2,662,822. to Edwin H. Land.

In particular, the novel silver halide developing agents of the present invention are highly useful in so-called The speed of a photosensitive material comprises generally an empirically derived relative measurement which may be defined as a value representing the reciprocal of the exposure required to produce a given result. Any precise definition of speed, therefore, is based upon the selection of a particular result as the standard reference point. A precise quantitative measure of speed has been developed from the work of L. A. Jones et al., as reported in Mees, The Theory of the Photographic Process, the Macmillan Company, New York, 1944, Chapters XIX and XXII. This work suggested a system in which negative sensitive materials are assigned a speed that is in terms of the exposure required to give a negative image from which a positive print of specified quality can be produced.

Based on this work, The American Standards Association, Incorporated, has established standards for rating sensitive materials for speed. Under such standards, emulsion speed is considered as a value inversely proportional to the minimum exposure which must be incident upon the negative material, from the scene element of minimum brightness in which detail is visible, in order that a print of excellent quality can be made from the resultant negative. These standards specify techniques for plotting the characteristic H and D curve of a negative material, that is, the curve relating the logarithm of the original exposure of the negative to density in said negative. The value of speed derived from the standard characteristic curve so determined is specified as equal to the reciprocal of the exposure, E, on the characteristic curve at which the slope is 0.3 time the average slope for a log exposure range of 1.5 of which E is the minimum exposure. The precise method for determining speed in this manner is described in detail in the publication of The American Standards Association, Incorporated, PH 2.5, 1954, and titled American Standard Method for Determining Photographic Speed and Exposure Index.

The A.S.A. speed rating is to be distinguished from what is termed the A.S.A. Exposure Index, for use with exposure meters and calculators. The A.S.A. Exposure Index is determined by the formula: A.S.A. Exposure Index=A.S.A. Speed/ 4. The exposure index so obtained indicates generally the correct exposure rating to which an A.S.A. calibrated exposure meter must be set in order that it give correct exposure data for producing pictures of satisfactory high quality.

The A.S.A. speed rating is to be further distinguished from what may be termed Diifusion Transfer Process Exposure Index. In such processes, the exposure index may be based on a curve relating original exposure of the negative to the density in the resultant positive. It has been found experimentally that the Diffusing Transfer Exposure Index of a silver transfer process may be determined by plotting a characteristic curve of the reflection density of the positive as a function of the log exposure of the negative, determining the exposure in meter-candleseconds (m.c.s.) at the point on this curve corresponding to a density of 0.50, and dividing the constant 4.0, by the exposure so determined. The exposure index so obtained indicates generally the correct exposure rating of a silver transfer process to which an exposure meter, calibrated to the A.S.A. Exposure Index, must be set in order that it give correct exposure data for producing transfer prints of satisfactory high quality, and is sometimes referred to as the Equivalent A.S.A. Exposure Index.

7 Both the A.S.A. Exposure Index and the Difiusion Transfer Exposure Index can be judged or rated according to sensitometric criteria with exposure, that is, the luminance flux reaching a unit area of the photosensitive surface, being measured in m.c.s The equivalence of the foregoing methods of determining rated A.S.A. Exposure Indices and Diifusion Transfer Exposure Indices can be readily established by obtaining a standardized silver transfer positive and determining the illumination, by measuring with an exposure meter calibrated according to an A.S.A. standard which includes a computer in which has been entered the shutter duration and f-stop of the camera, found necessary to provide the standard transfer print.

In the subsequent discussion, the term A.S.A. Exposure Index is intended to signify the exposure index determined in accordance with the aforementioned American Standards Association specifications. The term Diffusion Transfer Exposure Index is intended to signify, in reference to diifusion transfer processes, or the materials used therein, the exposure index as determined in the aforementioned manner. Both designations, in one sense, serve the same purpose. The A.S.A. Exposure Index of the negative is based upon the exposure to which the negative must be subjected in order to obtain a good photograph of a predetermined subject by conventional processing, Whereas the Diffusion Transfer Exposure Index is based upon the exposure to which a negative for use in a silver diffusion transfer process must be subjected in order to obtain a good by positive by that process. Both, therefore, are direct guides to the exposure setting which must be made in a camera in order to obtain proper exposure. Nevertheless, the two definitions of exposure must be carefully distinguished from each other because, although the A.S.A. Exposure Index is related qualitatively to the production of a positive of high quality, it is a term which describes the character of a negative material. The negative material, nevertheless, may be employed, for example, in a silver diffusion transfer process of the present invention to effect a Difiusion Transfer Exposure Index vastly different from the A.S.A. Exposure Index of the negative material. In the novel diffusion transfer processes of the present invention, a positive print of satisfactory high quality is produced from a negative material subjected to exposures less, in some cases many times less, than recommended by its rated A.S.A. Exposure Index. Such an exposure provides a latent image having a density gradient confined to the low exposure or toe region of the negative materials characteristic curve.

Referring now to the drawing, FIGURE 1 illustrates one assemblage and process of the present invention in the performance of a diffusion transfer process for the production of positive silver prints. As depicted in the drawing, an aqueous alkaline fluid layer 12 of a silver halide developing agent chosen in accordance with the present invention and a suitable silver halide solvent are spread betwen photosensitive emulsion layer 11 which is superposed on support 10 and image-receiving layer 13 which is affixed to support layer 14. Image-receiving layer 13 preferably contains silver precipitating agents or nuclei such as the silver precipitating nuclei disclosed in U.S. Patent No. 2,698,237. Support layer 14 may comprise an opaque material where a reflection print is desired or may comprise a transparent material Where a transparency is desired.

Fluid layer 12 may be obtained by distribution of the processing composition in a substantially uniform manner between photosensitive emulsion layer 11 and image-receiving layer 13, for example, in accordance with the procedures disclosed in U.S. Patent No. 2,543,181. For example, one or more rupturable containers may be attached to either photosensitive emulsion layer 11 and/ or image-receiving layer 13 such that upon superposition of the respective layers 11 and 13 said container or containers are so positioned as to be capable, upon rupture, of releasing their contents in a substantially uniform layer between and in contact with the opposed surface of 'each of said layers. Rupture of the container or containers and spreading of the contents thereof may be accomplished, for example, by compression between a pair of opposed, suitably gapped, rollers.

For clarity, the particular developer selected, the degree to which the photosensitive layer is exposed, and the character of the silver-receptive layer will be described in detail hereinafter.

The processing composition preferably comprises a filmforming transfer processing composition. It may comprise, for example, one or more of the previously enumerated developing agents of the present invention, an alkali such as sodium hydroxide, a silver halide complexing agent such as sodium thiosulfate, and a high molecular weight film-forming thickening agent such as sodium carboxymethyl cellulose. All these materials are preferably in aqueous solution. These photographic agents are preferably contained in solution in theprocessing composition prior to the spreading thereof as layer 12, but they may be in part or in whole added to the processing composition as it is spread between the photosensitive emulsion 11 and image-receiving layer 13, said agents being so located on, in, or adjacent to a surface of one or both of said layers as to be dissolved by or otherwise interacted with the liquid agent when the latter wets said layers.

In carrying out the aforementioned transfer process, the photosensitive emulsion 11 is exposed to a predetermined subject matter to form therein a latent image of said subject matter. The exposed emulsion is superposed on image-receiving layer 13 and the photographic processing composition 12 spread between the opposed surfaces of said emulsion 11 and said image-receiving layer 13. Reagents permeate into the photosensitive emulsion 11, developing the latent image contained therein and forming a soluble silver complex of unexposed silver halide. Soluble silver complex is transported from photosensitive emulsion layer 11, at least in part, by imbibition, to printreceiving stratum 13 and the silver of the complex is precipitated thereon and/or therein to provide the desired positive image formation. The laminate formed by the spreading of the processing composition as layer 12 between photosensitive emulsion layer 11 and print-receiving layer 13 is kept intact for approximately /2 to 1% minutes, preferably 1 minute, and at the termination of this time interval the print-receiving layer 13 is dissociated from photosensivtive emulsion 11 as, for example, by manual stripping.

A further transfer process of the present invention for the production of positive silver prints is illustrated in FIG. 2 and comprises a spreader sheet 15, a layer of relatively viscous processing composition 12, a photosensitive gelatin emulsion layer 11 superposed on image-receiving layer 13 which is, in turn, superposed on a support layer 14. As stated in connection with the description of FIG- URE 1, image-receiving layer 13 preferably contains silver precipitating nuclei and support layer 14 may comprise either an opaque or transparent material.

Fluid composition layer 12 may be obtained by spreading a photographic processing composition, for example, in a manner disclosed in U.S. Patent No. 2,698,244. As disclosed in the aforementioned patent, the liquid processing composition may be disposed in a rupturable container so positioned in regard to the appropriate surface of photosensitive emulsion layer 11 that, upon compression by spreader sheet 15, a substantially uniform layer 12 of processing composition is distributed over the external surface of said photosensitive emulsion 11, with respect to image-receiving layer 13.

In carrying out the last-mentioned transfer process, the photosensitive emulsion 11 is exposed to a predetermined subject matter to form therein a latent image of said sub ject matter. A substantially uniform distribution of processing composition 12 is distributed on the external surface of said emulsion 11, as for example, according 9 to the previously described procedure. Processing composition reagents permeate into photosensitive emulsion 12, developing the latent image contained therein according to the point-to-point degree of exposure thereof. Substantially contemporaneous with the development of the latent image, an irnagewise distribution of soluble silver complex is formed from unexposed and undeveloped silver halide within said emulsion. At least part of said silver complex, solubilized, is transferred, by imbibition, to print-receiving stratum 13. The transferred silver complexes are reacted therein to provide a positive, reversed image of the latent image. Subsequent to formation of the positive image in image-receiving layer 13, dissociation of said layer from emulsion layer 11 may be effected.

Where desired, the image-receiving layer 13 may be dissociated from emulsion layer 11 by stripping the emulsion from the surface thereof. A conventional stripping layer may be provided to facilitate separation of emulsion layer 11 from image-receiving layer 13 subsequent to transfer processing. Sufficient abrasion-resistant properties may be provided to image-receiving layer 13 as to alleviate any necessity of subsequently overcoating the external surface of said image-receiving layer 13 with a transparent abrasion-resistant water-soluble plastic to prevent subsequent laceration and resultant degradation of the positive image. Image-receiving layer 13 may also comprise sufficient integral dimensional stability as to alleviate the necessity of a separate support layer 14.

In the last-mentioned processes, spreading of the liquid processing composition on the external surface of photosensitive emulsion layer 11 is preferably effected by rupture of a suitably positioned frangible container and distribution of its processing composition contents by means of a converted cellulose acetate spreader sheet, that is, a cellulose acetate sheet the surface of which has been converted to cellulose. When employed, the converted cellulose acetate spreader sheet may exhibit an adhesive capacity for the processing composition in excess of the adhesive capacity exhibited by the photosensitive emulsion. A means is thus provided foreffecting dissociation of the processing composition from contact with the photosensitive emulsion, subsequent to image formation, by dissociating the spreader sheet from its proximate relationship to the external emulsion surface.

It will be apparent that the facility with which the photosensitive emulsion layer is dissociated from contact with the print-receiving layer may be increased by providing a conventional stripping layer interposed between said emulsion and said print-receiving layer. The stripping layer may be coated on the surface of the printreceiving element and a photosensitive emulsion thereafter coated on the external surface of said stripping layer.

While distribution of the processing composition in diffusion transfer processes has been described utilizing a frangible container, it will be apparent that said container provides a convenient means of distributing the liquid processing composition to permit the processing to be effected within a suitable camera apparatus. The diffusion transfer process of this invention may be otherwise effected. For example, a photosensitive element, after exposing a suitable apparatus and while preventing further exposure thereafter to actinic radiation, may be removed from such apparatus and permeated with the liquid processing composition as, for example, by coating, spraying, flowing etc., the composition on said photosensitive element or otherwise wetting said element with a composition, following which the permeated, exposed, photosensitive element, still without additional exposure to actinic radiation, is brought into contact with the image-receiving element for image formation in the manner heretofore described.

The rupturable containers may be constructed in accordance with the disclosures set forth inU.S. Patent No. 2,634,886. Containers of this type are generally constructed from a blank comprising a flexible, deformable,

three-ply sheet material comprising, respectively, an outer layer of kraft paper, a layer of metal foil and an inner layer or liner of a thermoplastic resin. The container blank is folded upon itself such as to provide a fluid-containing cavity and a container exhibiting a sealed passage adjacent to an edge thereof which may be substantially uniformly unsealed throughout a predetermined length of the seal passage upon application of stress to the container. The passage may be formed by the utilization of differential adhesion.

As previously noted, the print-receiving stratum preferably contains silver precipitating agents or nuclei, whose presence during the transfer process has a desirable effect on the amount and character of the silver precipitated during positive print formation. Examples of such silver precipitating agents are the metallic sulfides and selenides, thiooxalates, and thioacetamides, and colloidal metalsdisclosed in US. Patent No. 2,698,237. It is also desirable, as disclosed in that patent, to provide as the vehicle for the silver precipitating agents, a macroscopically continu ous film that consists of submacroscopic agglomerates of minute particles of a suitable water-insoluble, inorganic, preferably siliceous, material such as silica aerogel. The use of such a vehicle for the precipitating agents tends to aggregate the silver that is precipitated into its most effective condition for print formation.

Silver halide solvents suitable for incorporation in the processing composition include conventional fixing agents such as sodium thiosulfate, sodium thiocyanate, ammonium thiosulfate, or associations of cyclic imides and nitrogenous bases such as associations of barbiturates or uracils and ammonia or amines. Of these, the conventional fixing agents specifier are preferred. Preferably, the solution also contains a film-forming material such as a watersoluble plastic, starch or gum imparting a viscosity of from 1000 to 200,000 centipoises at a temperature of 20 C. in order to permit the solution to be readily controlled during and after spreading.

It will be apparent that the relative proportions of the agents of the developer composition set forth herein may be altered to suit the requirements of the operator. Thus, it is within the scope of this invention to modify the herein described developing compositions by the substitution of preservatives, alkalies, silver halide solvents, etc., other than those specifically mentioned. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of developing agent may be varied over a wide range and when desirable the developing agent may be disposed in the photosensitive element prior to the exposure of the emulsion. The developing agent may be disposed in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The emulsion support layer designated in the drawing as 10 may comprise any of the various types of conventional rigid or flexible supports, for example, glass, paper, metal, and polymeric films of both the synthetic types and those derived from naturally occurring products.

The photosensitive emulsion stratum may comprise a commercially available silver halide gelatin emulsion such as Microfile, Spectrum Analysis, Contrast Process, S XX Aero Recon, Verichrome, Royal Pan, Royal X Pan, Tri X Pan, Fine Grain Pan, High Speed Pan, Arrow Pan, Superior 3, Triple S Pan, or Gevapan.

Of the developing agents of the present invention, compounds wherein either R or R comprises a hydroxybenzyl group possess specific and unexpected advantages. These compounds are characterized by unexpectedly higher process speeds when employed in diffusion transfer processes. The higher process speeds may be the result of a solubilizing effect imparted to the developer molecule by the hydroxyl group substituted on the benzyl group.

The compounds of the present invention may also be used in small quantities with other silver halide developers, for example, hydroquinone or one of its derivatives, to produce high speed prints of exceptional quality by diffusion transfer processes.

in accordance with the present invention lies at a relatively low exposure level and corresponds to an exposure gradient predominantly below approximately 0.015 m.c.s. Ordinarily, the fog level in such a case is at a point on The present invention will be illustrated in greater dethe characteristic curve that corresponds to an exposure tail in conjunction with the following specific examples gradient predominantly above approximately 0.005 which set out representative use of the novel silver halide mos. developing agents of this invention in high speed diffusion As used herein and in the above table, the shoulder transfer processes, which however are not limited to the speed is the minimum amount of exposure in meterdetails therein set forth and are intended to be illustracandle-seconds which can be used to expose the negative tive only. emulsion and give a transfer image in which there is The indicated developing agents employed and the rethe minimum contrast which the eye can distinguish, i.e., sults obtained in the specific examples are hereinafter there is visible detail in the shadow regions of the transset forth in tabular form. (Specific examples employing fer image. This exposure level is determined at the point metol, amidol and hydroquinone, respectively, have been 15 on the shoulder portion of the previously described charreported for the purpose of providing comparative data.) acteristic curve of the positive transfer image where the A silver iodobromide emulsion having the designated SlopeiS 0.4.

A.S.A. Exposure Index is exposed to a predetermined As illustrated in the aforementioned specific examples subject through a stop which gives rise to the indicated the photosensitive emulsions of the present processes are Diffusion Transfer Exposure Index, advanced in superunderexposed in relation to their respective A.S.A. Exposed relationship with an image-receiving element, composure Index to produce therein a weak latent image prising asilver-receptive stratum containing silver precipihaving an exposure gradient predominantly in the toe tating nuclei dispersed in a matrix of colloidal silica region of the ASA. density versus log exposure curve of coated on a water-impervious base according to the practhe photosensitive emulsion. The emulsion is therefore tice described in US. Patent No. 2,823,122, issued to exposed to produce alatent image lvingin the toe region Edwin H. Land on February 11, 1958, between a pair of of the A.S.A. characteristic curve for the negative emulpressure-applying rollers to spread a processing composiiOn S c that, y the Standard development tion comprising: method, it would be impractical to develop the emulsion such as to provide a useful conventional negative image. Water 398 B means of the com ositions roducts and rocesses of Carboxymethyl cellulose (high viscosity) grams 15.25 y P P p Sodium sulfite do 25 6 the present invention, one may advantageously employ a photosensitive emulsion having a stated A.S.A. Exposure Sodium hydroxide do 15.2

Index and provide said emulsion with an effective ex- Sodium thiosulfate do 5.4 emitmbenzimidazole do 0 5 posure that ordinarily would require a photosensitive emulsion having a higher A.S.A. Exposure Index to proand a concentration of the specified developer designated vide an acceptable positive print resultant therefrom. in the following table, between the photoexposed emul- With conventional developing practices, good negatives sion and the image-receiving element in a thin layer apcan be obtained only from an emulsion that has been proximately 0.003 of an inch thick. After an imbibition sufiiciently exposed within the range of exposures speci period of approximately seconds, the emulsion, tofied for the emulsion. Underexposed emulsions result in gether with the layer of processing composition, is a negative having only an image from which it is impracstripped from the image-receiving element to uncover the tical to obtain a satisfactory print by conventional proc positive print, which provided satisfactory contrast, denesses. sity and range. The present invention obviates the problem of construct- Ooncentra- Diffusion Emulsion tion (grams! Imbibition Density Density Transfer A.S.A. Shoulder Compound 10 00. pro- Time (maximum) (minimum) Slope Exposure Exposure Speed cessing oom- (minutes) Index Index (m.c.s.)

position) 0.4 1 1.40 0. 01 2.02 2,000 200 0.00040 0.4 1 0.82 0.01 0. s0 9, 000 ca. 800 0.00022 0.4 1 1. 07 0. 01 1.18 109 200 0.0030 0.4 1 1.31 0. 03 0. 90 180 ca. 800 0.0024 0.4 1 1. 07 0.03 1. 38 1, 420 200 0. 00035 0.4 1 1. 43 0. 00 1.24 7, 520 ca. 800 0. 000098 0.4 2 1.00 0.30 0.42 072 200 0.00078 0.2 2 1.58 0.20 2.10 1,120 200 0. 00074 0.2 2 1. 00 0.02 0.84 10,000 ca. 800 0.00018 0.4 1 1.38 0.00 1.14 8,800 ca. 800 0.000080 04 1 1.08 0. 00 0.70 5, 840 ca. 800 0.00011 0.4 1 1. 00 0.06 0.00 8,400 ca. 800 0.000080 0.4 2 1.10 0. 01 1.34 1, 840 200 0.00064 1 Processing composition contains an additional 1% sodium thiosulfate. l The emulsions possessing an A.S.A. Exposure Index of 200 are coated on a transparent film base; the specific figure 200 represents the A.S.A. Exposure Index designated by the emulsion manufacturer.

The emulsions possessing an A.S.A. Exposure Index of ca. 800 are coated on the external surface of a reflecting layer which is on a paper base; the A.S.A. Exposure Index ca. 800

was determined experimentally.

The chief function of a photographic negative material as used in pictorial photography is to reproduce as density differences the luminance differences existing in the object photographed. The minimum useful exposure will, therefore, be that required to reproduce the minimum difference existing in the shadow regions of the object by means of some minimum density difierence in the resulting image.

When the novel developing agents of this invention are used in high speed diffusion transfer processes, the region of the ASA. characteristic curve of the negative used ing a satisfactory negative from an underexposed emulsion, for example, by intensification, hypersensitization, latensification techniques, so as to obtain a satisfactory positive print. In addition, the present invention provides satisfactory positive images from both underexposed and adequately exposed conventional silver halide photosensitive emulsions. As previously mentioned, a convenient measure of the amplification of image development, obtained according to the present disclosure, over the results obtained from conventional development practices, is in terms of increase in the speed or quantum excitation 13 sensitivity of the emulsion as indicated by the results previously set forth, over the normal specified speed of the same emulsion as determined by the results of standard development practice.

Since certain changes may be made in the above products, processes and compositions without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A compound selected from the group consisting of compounds of the formula:

wherein one of R and R is a hydroxybenzyl group and the other of R and R is hydrogen; and Z is selected from the group consisting of hydrogen and chlorine.

2. 4-amino-2- p-hydroxybenzylamino -phenol.

3. 4-arnino-2-(m-hydroxybenzylamino)-phenol.

4. 2-amino-4-(m-hydroxybenzylamino)-phen0l.

5. 2-amin0-4-(p-hydroxybenzylamino)-phen01.

6. 4-amino-6-chloro-2-(p-hydroxybenzylamino) phe- 1101.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. PARKER, Primary Examiner. 

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF THE FORMULA: 